Create python bindings of VectorsCollection

[FabioBergonti]

My previous PR #850 was not working as expected because I forgot to create the bindings for VectorsCollection. In particular, when you call read_data you get the following error:

TypeError: Unable to convert function return value to a Python type! The signature was
        (self: bipedal_locomotion_framework.bindings.yarp_utilities.VectorsCollectionClient, arg0: bool) -> BipedalLocomotion::YarpUtilities::VectorsCollection

This PR creates Python bindings for VectorsCollection and modifies the behavior of read_data to provide an empty collection as output when it is unable to retrieve data.